This invention relates to the field of body armor and in particular to the use of a desiccant in combination with the ballistic material of body armor in order to maintain humidity in the body armor beneath performance reducing levels.
P-phenylene-2,6-benzobisoxazole, referred to herein and by one manufacturer, Toyobo Co., Ltd. of Osaka, Japan, by the acronym PBO and sold by that manufacturer under the trademark Zylon, is advertised as a rigid-rod lyotropic liquid crystal polymer having tensile strength and modulus superior to P-Aramid fibres, and as exhibiting outstanding high flame resistance and thermal stability among organic fibres. In applicant's experience, use of Zylon™ in ballistic body armor may provide up to approximately thirty percent better performance as compared to, for example, older aramid ballistic materials. Zylon™ is thus now a commonly used ballistic material in body armor design because of its improved performance to protect against penetration by ballistic projectiles such as bullets. However, it is now been identified that Zylon™ degrades under combined high heat and high humidity conditions so as to adversely affect its ballistic performance. The degradation is not, as far as applicant is aware, the impermanent performance degradation such as has been previously identified due to moisture in the use Kevlar™ woven aramid fibre cloth, but rather results in permanent degradation of the ballistic material performance. In applicant's experience, and in applicant's prior art designs such as sold by Pacific Safety Products of Kelowna, British Columbia, Canada, applicant and other designers of ballistic armor take extreme care in the design of, and rigorously test, any changes to the order, number and composition of the layers of material found with ballistic body armor. A user's life may depend on it. Consequently, the introduction by a person skilled in the art of flexible ballistic body armor of a substance or layer into the ballistic material layers which is foreign to conventional substances or layers conventionally found in ballistic body armor is in applicant's experience rarely done. Changes and modifications are only very conservatively implemented to avoid chances of unforeseen adverse consequences to the ballistic performance of the layers of ballistic material whether they be woven aramid fibre layers or the PBO layers which are the subject of the present invention. Applicant's invention is thus unconventional in that at least one layer of a foreign desiccant substance, for example at least one layer of desiccant sheet is interleaved, sandwiching, or sandwiched between the layers of conventional PBO ballistic material in flexible ballistic body armor. It is an object of the present invention to introduce a desiccant into ballistic body armor employing PBO fibre ballistic body armor so as to inhibit permanent performance degradation of the material's ballistic penetration resistance due to moisture within the body armor. In the prior art, applicant is aware of patents disclosing the use of moisture control materials in protective clothing for the purposes of the comfort of the wearer. In particular, applicant is aware of patents which disclose the use of wicking and other materials to transfer, evaporate or absorb moisture within the garment, as for example found disclosed in U.S. Pat. No. 6,044,498 which issued to Schumann et al. on Apr. 4, 2000 for Slash and Cut Resistant Garments for Protecting a Person From Injury, U.S. Pat. No. 5,471,906 which issued Bachner, Jr. et al. on Dec. 5, 1995 for a Body Armor Cover and Method for Making the Same, U.S. Pat. No. 5,327,811 which issued to Price et al. on Jul. 12, 1994 for a Lightweight Ballistic Protective Device, U.S. Pat. No. 5,472,769 which issued to Goerz, Jr. et al. on Dec. 5, 1995 for a Soft Body Armor Material with Enhanced Puncture Resistance Comprising at Least One Continuous Fabric Having Knit Portions and Integrally Woven Hinge Portions, U.S. Pat. No. 6,233,737 which issued to Ditchfield et al. on May 22, 2001 for a Concealable Ballistic Vest and U.S. Pat. No. 6,138,277 which issued to Gillen et al. on Oct. 31, 2000 for a Protective Body Vest. The moisture control in this prior art generally involves the use of fabric layers for example the moisture absorbing inner layer of Goerz, Jr., or the vapour permeable cover layer over the flexible armor plating layer of Bachner, Jr. et al. Similarly, in the prior art applicant is also aware of a Korean Patent, Patent No. KR 2001017116 which issued to Lee for a Bulletproof Vest Having Air Ventilation Property and which discloses the use within a bulletproof vest of inner covers of foamed polyethylene material providing such an air ventilation property so that sweat moisture is transferred from the body of the user to a moisture absorbing fibre positioned inside an outer cover.